He doesn't think he is trading stocks; He always invests. His original intention of buying stocks is not to sell them after buying them, but to hold them forever. Do you still think he is a stock trader? At least it's not the same meaning as everyone understands.
Of course, listed companies can raise funds, but I don't think Buffett usually uses this method. For him now, the cost of using insurance will be lower. The cost of equity financing is too high. In a mature market, unlike here, offering returns to those shareholders is much higher than borrowing money. With Buffett's reputation, it is better to borrow money by issuing stock financing.